<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
        // var str='123';
        // console.log(Boolean(''));

        // var num=NaN;
        // console.log(Boolean(num));

        // var list=[];
        // console.log(Boolean(list));
        //数组的对比
        // console.log(list==true);

        // var str='';
        // console.log(!!str);

    </script>
</body>
</html>